OMG S’mores Bars (Gooey Marshmallow Fluff Bars)

As an Amazon Associate, I earn from qualifying purchases. Read the full disclosure here.

Brace yourself… these OMG S’mores Bars are coming in hot, gooey, and dangerously irresistible. We’re talking layers of buttery graham cookie dough, melty Hershey bars, and billowy marshmallow fluff baked into the most addictive s’mores dessert ever.

No campfire needed — just pure, over‑the‑top s’mores bliss in every bite, the kind that makes you want to explore every s’mores dessert you can get your hands on.

Why You’ll Love These Marshmallow Fluff S’mores Bars

These OMG S’mores Bars take everything you love about a classic campfire s’more and turn it into a gooey, bakery‑style dessert you can make anytime. They’re thick, melty, and loaded with layers of buttery graham cookie dough, Hershey chocolate, and marshmallow fluff — no campfire required.

They slice beautifully, travel well, and always disappear fast at parties, potlucks, and summer gatherings. If you love easy dessert bars with big flavor payoff, these will absolutely woo you in… just like my S’more Cookie Bars, Best S’more Cookies this S’mores Cookie Cake, these S’more Cookies and this S’mores Poke Cake do.

These bars are a fun twist on the classic s’mores combo, but instead of using mini marshmallows, this recipe uses marshmallow fluff for that perfectly gooey, spreadable layer that melts like a dream. If you try them with actual marshmallows, report back — I’ve only ever made them with fluff because it gives the most consistent, irresistible texture.

Ingredient Notes

A quick look at what makes these smore bars so irresistible:

• Unsalted Butter Creates a soft, rich cookie dough base that browns beautifully in the oven.
• Brown Sugar + Granulated Sugar The combo gives the dough its chewy texture and caramel‑y flavor.
• Eggs + Vanilla Bind the dough and add that classic cookie‑dough warmth.
• All‑Purpose Flour Gives structure to the bars so they bake up thick and sturdy.
• Graham Cracker Crumbs The secret to that nostalgic s’mores flavor — they turn the cookie dough into a graham‑cookie hybrid.
• Baking Powder + Salt Lift and balance the dough so it’s soft, golden, and not overly sweet.
• Hershey’s Milk Chocolate Bars The iconic s’mores chocolate. They melt into perfect, silky layers. (Giant bars fit the pan beautifully.)
• Marshmallow Fluff Spreads easily, stays gooey, and won’t evaporate or scorch like mini marshmallows. It’s the key to that signature “OMG” gooey pull.

Ingredients You Need for OMG S’more Cookie Bars

lAYERED Hershey’s S’more Cookie Bar Recipe

• Unsalted butter
• Brown sugar
• Granulated sugar
• Eggs
• Vanilla extract
• All‑purpose flour
• Graham cracker crumbs
• Baking powder
• Salt
• 3 Giant Sized (7 oz each) Hershey’s Milk Chocolate Bars or 4 large (4.4 oz.) chocolate bars
• Marshmallow fluff

Instructions How to Make OMG S’more Bar Recipe 

1. Preheat oven to 350 degrees.
2. Lightly grease or spray with cooking spray a 9-inch x 13-inch glass baking pan and line it with parchment paper, so the paper hangs over the sides a little. Set pan aside.
3. In a separate bowl, whisk together the graham cracker crumbs, flour, baking powder, and salt and set aside.
4. Using a mixer, in a large bowl, mix together the softened butter, white sugar, and brown sugar for 1 ½ to 2 minutes.
5. Add in the eggs and vanilla and continue mixing until well incorporated and smooth.
6. Add in the dry mixture into the butter / sugar mixture. Beat to incorporate, just until all the ingredients come together.
7. Gather the dough into a ball and divide dough into 2 balls.
8. Take one of the balls and spread out into the prepared pan by smooshing it down so that it covers the bottom of the pan completely in an even layer.
9. Cover the dough with a single layer of the chocolate bars. 3 fits nicely.
10. Next, add the marshmallow creme to the top of the chocolate bars and spread out to sides of pan.
11. Lightly flour a board or counter top and smoosh or roll with a rolling pin, the other half of the s’mores cookie dough and make it/roll it the size of the your pan. I do it by placing the pan on top to get an idea about the size to get an idea. Slice the dough into strips and lay each piece on top of the fluff until you’ve covered it all as good as you can. Try to cover up all the marshmallow as good as you can, but it’s ok to have some marshmallow poking out. 
12. Place pan into your preheated oven and bake for about 30-35 minutes, until the top is golden brown.
13. After baked, transfer to cool completely on a rack.
14. When cool, slice and serve. Place any leftovers in sealed container.

Tips for Perfect OMG S’mores Bars

Use parchment paper for easy lifting. Line your pan so you can lift the entire slab out once cooled. This makes slicing clean, even bars a breeze.

Let them cool before cutting. The layers need time to set. Once cooled, use a sharp knife or stainless steel spatula for clean edges.

Serve at room temperature. This keeps the marshmallow gooey, the chocolate soft, and the cookie layer perfectly tender.

Don’t swap the fluff (unless you’re experimenting). Marshmallow fluff melts evenly and stays gooey. Mini marshmallows can evaporate or scorch — but if you try it, report back!

Great for parties. A 9×13 pan gives you about 28 bars — the perfect size for sharing, gifting, or feeding a crowd.

Variations

• Cookies ’n Creme S’mores Bars Swap the Hershey bars for Hershey’s Cookies ’n Creme for a fun twist.
• Peanut Butter Cup S’mores Bars Layer peanut butter cups under the fluff for a salty‑sweet upgrade.
• Dark Chocolate S’mores Bars Use dark chocolate bars for a richer, less‑sweet version.
• Crunchy S’mores Bars Add chopped Nestlé Crunch bars or mini chocolate chips for extra texture.
• Mini Marshmallow Version If you want to try it with actual marshmallows, use a generous layer of minis — just know they melt differently than fluff.

Serving Ideas

• Serve at room temperature for the best gooey texture.
• Warm individual bars in the microwave for 5–10 seconds for extra meltiness.
• Pair with vanilla ice cream for a full dessert moment.
• Cut into smaller squares for dessert boards or party trays.
• Wrap individually for bake sales or gifting.

How to Store OMG Hershey’s S’mores Bars

Room Temperature (best option): Store in an airtight container for 2–3 days. This keeps the marshmallow soft and the chocolate from hardening.

Refrigerator: Not recommended — the chocolate firms up and the texture changes.

Freezer: You can freeze them, but the marshmallow becomes chewy. If you do freeze:

• Wrap bars individually
• Store up to 2 months
• Thaw at room temperature

FAQs

Can I use mini marshmallows instead of fluff?

You can, but they melt differently and may disappear or scorch. Marshmallow fluff gives the most consistent gooey layer.

Can I make these ahead?

Yes! They’re even better the next day once the layers settle.

Why is my top layer cracking?

This can happen if the dough is rolled too thin or overbaked. A little cracking is normal and still delicious.

Can I use chocolate chips instead of bars?

You can, but chocolate bars melt into a smoother, more classic s’mores layer.

How do I get clean slices?

Let the bars cool completely, lift them out with parchment, and use a sharp knife or metal spatula.

As a cozy‑luxe baker who loves putting a fun twist on nostalgic desserts, I’ve adapted this s’mores bar recipe to create a version that’s extra gooey, chocolate‑forward, and completely irresistible. The layers of graham cookie dough, marshmallow fluff, and melty Hershey chocolate come together in a way that feels both familiar and elevated — the kind of treat that always gets recipe requests.

Whether you’re making these for a party, a family night, or just because you’re craving something indulgent, they deliver that same “OMG” moment every single time. If you give them a try, I’d love to hear how they turned out for you — your feedback helps me keep creating cozy, chocolate‑loaded desserts you’ll love.

Share this marshmallow fluff s’mores bars recipe on Pinterest, Instagram and Facebook!

More Yummy Treats!

• Reese’s Peanut Butter Cup Explosion Brownies
• ‘Symphony’ Almond Toffee Milk Chocolate Chip Cookies
• Texas Sheet Cake
• S’mores Graham Cereal Bars
• 20 Gooey Chocolatey S’more Desserts
• Reese’s S’mores Graham Cracker Candy
• Perfect Hershey’s Chocolate Cupcakes
• S’more Ice Cream Cake
• Sheet Pan Confetti Cadbury Chocolate Easter Egg Cookie Bars
• Salted Caramel Pretzel & Peanut Dark Chocolate Brownies

Recipe from The Hungry Mouse